How to build an API with NodeJS and test it using Jest and supertest. Mocking is the act of replacing a function with a fake copy. vnglst.json) file in a folder __mockData__. You can now run the Jest test runner: $ npm run test Test Setup { expect(add(2, 3)).toBe(5); }); We test the add() method with test() function. Install the create-react-app and create the app: This should open a browser window with a spinning React logo. Solution. } Jest is a JavaScript test runner, that is, a JavaScript library for creating, running, and structuring tests. Let’s set this up! Run your tests using Jest: jest to run them once or jest --watchAll to enable watch mode. I hope you enjoyed this tutorial and feel free to ask me any questions. In our test we can mount the component and then assert on the output. return ( The Jest tool from Facebook suports a style of testing called snapshot testing, where basically: 1. Object.keys(user).map(key => renderLine(user, key)) Click below to add additional parameters. We’ll be using rest.js for the making the API requests. a payment API that does not offer you a sandbox server), however, I try to keep the integration testing system as close as possible to reality. Congratulations, you’ve now got Jest up and running and are ready to start writing some tests! Jest is a wonderful testing library created by Facebook to help test JavaScript code, React components, and much more. We can use Jest to create mocks in our test - objects that replace real objects in our code while it's being tested. Click through for source. ). And mocking props in jest/enzyme is easy. However when you start adding Redux, Api calls and Context it becomes a different story. This tutorial is based upon the async example by the creators of Jest (and their example is probably better ). Be sure to also check out their other examples. Jest is an amazing test runner and has some awesome assertion APIs built in by default. You should see a simple list with my profile data. vnglst.json) file in a folder __mockData__. In this tutorial I’ll give a quick and simple demo of it’s mocking capabilities for testing async functions. The code to unit test the API; Problem. Installation The first thing we'll want to do is install jest-expo, it's a Jest preset that mocks out the native side of the Expo SDK and handles some configuration for you. create-react-app sets up a dummy test for us in the app.test.js file. Let’s test this quickly in the browser. When writing unit tests you always test only the logic in the current method. Be sure to also check out their other examples. To begin with, I'm going to create a new test file to cover off the logic we are about to extract. Test Runner - a library or tool which picks up source code (tests) in a given directory or file, executes the test and write the result to the console or any specified location, example Jest, Mocha. You can find me on Twitter as @vnglst. You write a snapshot test and run it. I’ve used my own Github username and data as an example here, but you can add as many example data as you need for your tests: To let Jest mock the request module, you have to add the following line to github.test.js file: Now the simple unit test should pass and you’re ready to write more complicated tests! Having unit tests reduces development time in the future by Bhuman Soni. It’s often used for testing React components, but it’s also a pretty good general purpose testing framework. You check the snapshot into source control. That means we need to mock the fetch request and substitute a response. Create a new folder api in the folder src and add the file github.js with the following code: Then also add request.js with the following code: You’re now ready to make API requests using: github.getUser(‘vnglst’). constructor (props) { Your goal when writing integration tests is to t… We’re a part of the @AMI family. API automation testing should cover at least following testing methods apart from usual SDLC process . This definitely makes your tests easier to write and more readable: Hacker Noon is how hackers start their afternoons. Again, let's start with a test (act API on ReactDOM). This article was also published on my own personal blog. 12:31. Jest is a great JavaScript testing framework by Facebook. Mocking Fetch API calls with Jest. It’s often used for testing React components, but it’s also a pretty good general purpose testing framework. All you gotta do now is mock a request and write your test. This article was also published on my own personal blog. You should see a simple list with my profile data. If they don’t match, the test fails. If you enjoyed this story, we recommend reading our latest tech stories and trending tech stories. Mocking async function (like API calls) instead of testing with a real API is useful for a couple of reasons: It’s faster: you don’t have to wait until the API response comes in and you don’t have to deal with rate limits.It makes your tests ‘pure’, i.e. The first parameter is the name of the test, the second parameter is the function to be run. Also under the alias: .it.test.only to only run the parameterised tests . The purpose of rest api testing is to record the response of rest api by sending various HTTP/S requests to check if rest api is working fine or not.